1. Field of the Invention
The present invention relates to a display device including a display panel such as a matrix-type plasma display panel (hereinafter referred to as a PDP).
2. Description of the Related Background Art
In recent years, the size of display devices is becoming increasingly great, and the increase in the display device size has created a need for a reduction in the display device thickness. To meet such a requirement, various thin types of display devices have been developed and are practically used. A display device using an AC (Alternate Current) PDP is one of promising thin types of display devices.
A PDP includes a plurality of column electrodes (address electrodes) and a plurality of pairs of row electrodes extending in such a manner as to cross the column electrodes. The row and column electrodes are covered with a dielectric layer such that the surfaces thereof are not directly exposed in a discharge space. A discharge cell serving as one pixel is formed at each intersection between the row electrode pairs and the column electrodes. In the PDP, light is emitted by using a discharge, and each discharge cell can be only in either a state in which light is emitted or a state in which no light is emitted. In the PDP, multiple luminance levels are achieved by means of a subfield method, to represent halftone in accordance with an input video signal. In the subfield method, each field display period is divided into N subfields, and a number of times light is emitted for each subfield is determined depending on a weighting factor for performing light emission.
However, in the display device using the subfield method, the number of times light is emitted is determined in a fixed manner depending only on the weighting factor for each subfield, and the manner of determining the number of times light is emitted is not changed in any situation. This can cause a displayed image to become very dazzling when the luminance of light emission becomes high on a screen all over.
One known technique of avoiding the above problem is to use an automatic brightness limiter (ABL controller) for limiting the screen luminance in the display device based on the subfield method as in other types of display devices such as a CRT display. As a result of the luminance limitation, power consumption of the display device is limited.
The automatic brightness limiter limits the number of sustain pulses (the number of times light is emitted) in each subfield, based on luminance information (for example, an average luminance level) of an input image signal, thereby limiting the luminance level of the image signal.
However, in the display device in which power consumption is limited on the basis of the conventional technique, it is difficult to obtain not only optimal luminance but also good light emission efficiency.
It is an object of the present invention to provide a display device and a display panel driving method which each have a capability of limiting the power consumption of a driver circuit of a display panel and are each capable of displaying an image with improved luminance and increased light emission efficiency.
According to an aspect of the present invention, there is provided a display device comprising a display panel including a plurality of pairs of row electrodes between which a capacitive load is formed, and a plurality of column electrodes arrayed in the direction intersecting with the row electrodes so as to form discharge cells at respective intersections of the row electrode pairs and the column electrodes; a driver circuit for supplying a sustain discharge pulse between a pair of row electrodes by performing a process having: under a state fixed one row electrode for each of the pairs of row electrodes at a first potential in a light emission sustain period of the display panel, a first step of gradually changing the potential of the other row electrode for each of the pairs of row electrodes from the first potential toward a second potential by means of resonance between the capacitive load and a first inductor; a second step of fixing the other row electrode in the pair of row electrodes at the second potential; and a third step of gradually changing the potential of the other row electrode of the pair of row electrodes from the second potential toward the first potential by means of resonance between the capacitive load and a second inductor; and a power limiting circuit for limiting power consumption of the driver circuit, in accordance with luminance information of an input image signal; wherein when the power consumption of the driver circuit is not limited by the power limiting circuit, the driver circuit performs the second step before the potential of the other row electrode of the pair of row electrodes reaches the second potential at the first step, while when, the power consumption of the driver circuit is limited by the power limiting circuit, the driver circuit reduces the length of the period of the second step and performs the third step after completion of the reduced second step.
According to another aspect of the present invention, there is provided a method of driving a display panel having a plurality of pairs of row electrodes between which a capacitive load is formed, and a plurality of column electrodes arrayed in the direction intersecting with the row electrodes so as to form discharge cells at respective intersections of the row electrode pairs and the column electrodes, the method comprising: supplying a sustain discharge pulse between a pair of row electrodes by performing a process having, under a state fixed one row electrode for each of the pairs of row electrodes at a first potential in a light emission sustain period of the display panel, a first step of gradually changing the potential of the other row electrode for each of the pairs of row electrodes from the first potential toward a second potential by means of resonance between the capacitive load and a first inductor; a second step of fixing the other row electrode in the pair of row electrodes at the second potential; and a third step of gradually changing the potential of the other row electrode of the pair of row electrodes from the second potential toward the first potential by means of resonance between the capacitive load and a second inductor; performing the second step before the potential of the other row electrode of the pair of row electrodes reaches the second potential at the first step when power consumption is not limited; and reducing the length of the period of the second step and performing the third step after completion of the reduced second step when power consumption is limited.